1. Field of the Invention
The present invention relates to a watch case comprising a case middle, a rotary bezel, first angular positioning markings secured to the case middle, second angular positioning markings secured to the rotary bezel and elastic means tending constantly to place said first and second positioning markings in engagement with one another.
2. Description of the Related Art
A great many watch cases comprising a bezel mounted so that it can be turned are known. Such a bezel bears one or more indications that can be placed as desired in an angular position chosen from several determined angular positions, fixed by angular positioning markings kept in engagement by elastic return means. Some of these bezels can rotate in both directions. In this case, one of the problems is to contrive for the force necessary to overcome the return force exerted on the angular positioning markings to be more or less equal in both directions. This force has also to give the user the feel of handling a mechanism that offers a certain resistance to movement, but which is then smooth once this resistance has been overcome and continues to move practically by itself as far as the next angular position.
EP 0 686 897 has already proposed a solution to this problem using a positioning spring working with an internal tooth set of the rotating bezel. This positioning spring has two straight segments connected by a bowed segment, the free end of one of the straight segments is kept in engagement with the tooth set of the bezel by a bearing surface secured to the case middle and the free end of the other straight segment is secured to this same case middle. The spring is shaped so that the forces exerted by the tooth set on its end engaged therewith, in both directions of rotation of the rotary bezel, serve to increase (or decrease) the radius of curvature of the bowed segment of the spring and allows balancing of the forces in the two directions in which the bezel rotates.
Also proposed, in EP 1 139 185, is a watch case with rotary bezel in which the rotary bezel can be moved selectively into two vertical positions determined by stop elements. In one of these vertical positions, the bezel is able to turn, whereas in the other vertical position it engages with toothed sectors of a fixed annual member which prevents it from turning and holds it in a determined angular position.
Also proposed, in CH 536 509, is a device for the angular positioning of a rotary bezel able to require equal forces in both directions in order to turn the bezel. For this, an edge tooth set with triangular teeth, formed under the bezel, collaborates with a piston mounted in a housing belonging to the case middle. When the two faces of the triangular edge teeth have equal inclinations, the forces needed to turn the bezel in both directions are equal. Given the presence of a piston that has to be housed in the case middle, this solution is not easy to implement given the space occupied.